The trace fossil Cruziana semiplicata and the trilobite that made it

A set of criteria is suggested for associating a trace fossil with a plausible fossil: (1) close association in the field; (2) concurrent stratigraphic range; (3) a minimal choice of candidates available that could have made the trace; (4) consistent size range between trace fossil population and that of the maker; and (5) consistent biogeographic ranges for both. In the Upper Cambrian Andam Formation of Oman, there is a rare, direct association between trilobite body fossils and the trace fossil Cruziana in the same rock succession. An association of the trilobite Maladioidella cf. colcheni with the trace fossil Cruziana semiplicata is supported by the criteria listed. Maladioidella is associated with C. semiplicata over a wide geographical area in western Gondwana. It is therefore likely that some Cruziana species were made by trilobites.